NoteOn Smartpen (Unfinished)

NoteOn is a project to develop a small, self-contained smartpen. All currently available
smartpens require special paper or a base station that clips to the page, making
them inconvenient for quick notes and everyday use. NoteOn aims to be completely self-contained,
using inertial measurement to track pen movements.

That's the plan, anyway. NoteOn is on hold in the firmware development
phase. Getting the firmware working proved more difficult than I anticipated, and I lost
interest in the project as a result. At this point, I don't think I'll continue developing it.
Please feel free to develop or incorporate NoteOn into your own projects;
the design files are licensed CCv4-BY-SA,
and the firmware is licensed GNU GPLv3.

Currently, the electronic design of the first prototype has been completed, and
two prototype PCBs have been assembled. Drivers for all on-board peripherals
except the bluetooth transceiver have been written and tested.

This project was an entry in the 2014 Hackaday Prize,
in which it advanced to the semifinals.
As part of the entry, all project documentation is on Hackaday.io. Rather than repeat it
here, I refer you to the NoteOn project page.

Assembled prototype.

Assembled prototype with PCB shell removed.

Top view of PCB, with ICs annotated.

Assembled prototype PCBs 1 and 2. The wires attached to prototype
2 are for probing the SPI bus and on-chip bootloader.